No weeks. Pretty huge.
In theory, more working days per year. We are so used to the week system that it is hard to predict the effects, but I suppose that the reduced unitary productivity derived from the lack of rest may more than compensate the added working time. Said lack of rest might also cause more dissatisfaction among workers (it appears to have been a serious problem in Revolutionary France).
Also, IIRC, no leap years. They'd have to invent something to adjust the calendar to astronomical realities in the long run. The months' names would sound odd with climates different than France's but that's not a problem (month names from September to December bear an etymological relationship with Latin numerals that is still very apparent in Romance languages; but of course, the numeral in their name and their order confusingly don't correspond. We use those names regardless).
It's not like they had a five day work week and unions to enforce it in the 18th century.
Also September still corresponds as the seventh month from the start of the year when you start the year quite sensibly with a new season, ie in spring.